Congenital Phenotypes and DMPK CTG Repeat Number in Mothers/Children with Myotonic Dystrophy Type 1

Abstract

Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic disease often resulting in more severe symptoms in affected children. The number of CTG repeats is reportedly related to congenital myotonic dystrophy 1 (CDM) severity. In this study, we aimed to clarify whether the number of CTG repeats can predict the severity of symptoms in children with CDM. This retrospective study examined 14 women with DM1 and their 14 children diagnosed with CDM. There were 11 CDM and 3 non-CDM patients. The correlation between the mother and child’s CDM onset and CTG repeat numbers was analyzed. The<strong> </strong>mean CTG repeat numbers in women who bore a child with CDM (detected polyhydramnios during pregnancy; hypotonia, respiratory insufficiency, or suckling failure at birth; bilateral facial weakness; delayed motor and mental development; talipes; and other contractures) were significantly lower compared to those who bore a non-CDM child (620 ± 450 vs. 933 ± 57, respectively). However, there was no significant difference in the mean CTG repeat numbers between the children with and without CDM (1,617 ± 323 vs. 1,789 ± 428, respectively). Our results suggest that CDM cannot be predicted based on the CTG repeat number of the mother or child.